A5974ADTR STMicroelectronics, A5974ADTR Datasheet - Page 41

• Manufacturer Part Number: A5974ADTR
• Description: IC REG SW STEP-DOWN 2A 8SOIC
• Manufacturer: STMicroelectronics
• Series: -r
• Type: Step-Down (Buck), PWMr

Specifications of A5974ADTR

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 1.235 V ~ 35 V
• Current - Output: 2A
• Frequency - Switching: 500kHz
• Voltage - Input: 4 V ~ 36 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (0.154", 3.90mm Width) Exposed Pad
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: 497-11423-2

A5974AD
8.11
MLCCs (multiple layer ceramic capacitor) with values in the range of 10 µF-22 µF and rated
voltages in the range of 10 V-25 V are available today at relatively low cost from many
manufacturers.
These capacitors have very low ESR values (a few mΩ) and are therefore occasionally used
for the output filter in order to reduce the voltage ripple and the overall size of the
application.
However, the zero given by the output capacitor falls outside the designed bandwidth and so
the system becomes unstable with the standard compensation network.
Figure 30
capacitors at the output (the optimum components value depends on the application). This
configuration introduces two zeroes and a low frequency pole in the designed bandwidth
and so guarantees a proper phase margin.
Figure 30. MLCC compensation network circuit
External soft-start network
At startup, the device can quickly increase the current up to the current limit in order to
charge the output capacitor. If soft ramp-up of the output voltage is required, an external
soft-start network can be implemented, as shown in
up to an external reference through R and the BJT clamps the COMP pin.
This clamps the duty cycle, limiting the slew rate of the output voltage.
shows the type III compensation network stabilizing the system with ceramic
Doc ID 018762 Rev 1
Figure
31. The capacitor C is charged
Application information
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